GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) - Manual (Page 93)

If the control card is suspect, replace it in accordance with the disassembly procedures in Section 7 or 8.
Should the above tests check correctly, proceed to testing the SCR gate signals.
To view the gate signals, an oscilloscope and a current probe are required.
8. Run the frequency converter while under some degree of load. At least a 30% load may be required to consistently see gate signals produced since
SCRs are only gated when the DC bus falls below the peak of line.
9. Connect the current probe, in sequence, to each (+) positive SCR gate wire (white leads) marked R, S, and T at power card connector MK100.
The waveform should appear as in Illustration 6-16.
Illustration 6.16: SCR Gate Signal
The current pulse should have a waveform as shown.
A1 > 1.1 A
A2 > 0.40 A
T1> 300 μs
Given all the other tests above were successful, a missing gate signal indicates the power card is defective. Replace the power card in accordance with the
disassembly procedures in Section 7 or 8.
A distorted signal may be due to a defective gate on that particular SCR that is loading down the supply. Replace the SCR module which corresponds to the
incorrect gate signal reading.
6.3.10 Output Imbalance of Supply Voltage Test
Checking the balance of the frequency converter output voltage and current measures the electrical functioning between the frequency converter and the motor.
In testing the phase-to-phase output, both voltage and current are monitored. It is recommended that static tests on the inverter section of the frequency converter
be conducted prior to this procedure.
If the voltage is balanced but the current is not, this indicates the motor is drawing an uneven load. This could be the result of a defective motor, a poor connection
in the wiring between the frequency converter and the motor, or, if applicable, a defective motor overload.
If the output current is unbalanced as well as the voltage, the frequency converter is not gating the output properly. This could be the result of a defective power
card, gate drive, connections between the gate drive card and IGBTs, or the output circuitry of the drive improperly connected.
NB!
Use an analog voltmeter for monitoring output voltage. Digital voltmeters are sensitive to waveform and switching frequencies and commonly return erroneous
readings.
AF-650 GP and AF-600 FP High Power Service Manual
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